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33 Cards in this Set
- Front
- Back
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Cell Theory |
-The cell is the smallest structural and functional living unit -Organismal functions depend on individual and collective cell functions -Biochemical activities of cells are dictated by their specific subcellular structures -Continuity of life has a cellular basis |
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Cell Diversity |
-There is over 200 types of human cells -Each differ in size, shape, subcellular components, and functions |
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Plasma Membrane |
-Flexible outer boundary of cell -Bimolecular layer of lipids and proteins in a constantly changing fluid mosaic -Separates intracellular fluid from extracellular fluid |
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Cytoplasm |
Intracellular fluid containing organelles |
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Nucleus |
Control center of cell |
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Interstitial Fluid |
Extracellular fluid that surrounds cells |
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Membrane Lipids |
-75% phospholipids -5% glycolipids -20% cholesterol |
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Phospholipids |
-Composed of Phosphate head that are polar and hydrophilic and -Fatty acid tails that are nonpolar and hydrophobic |
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Glycolipids |
-Lipids with polar sugar groups on the outer membrane surface |
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Cholesterol |
-Increases membrane stability and fluidity |
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Lipid Rafts |
-Makes up 20% of the outer membrane surface -Contains phospholipids and cholesterol -May function as stable platforms for cell-signaling molecules |
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Membrane Proteins |
-Integral proteins -Peripheral proteins |
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Integral Proteins |
-Firmly inserted into the membrane -Function as transport proteins (channels and carriers), enzymes, or receptors |
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Peripheral Proteins |
-Loosely attached to integral proteins -Includes filaments on intercellular surface and glycoproteins on extracellular surface -Functions include: Enzymes, motor proteins, cell-to-cell links, provide support on intracellular surface, and form part of glycocalyx |
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Functions of Membrane Proteins |
-transport
-receptors for signal transduction -attachment to cytoskeleton and extracellular matrix -enzymatic activity -Intercellular joining -Cell-cell recognition |
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Types of membrane junctions |
-Tight junction -Desmosome -Gap junction |
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Tight Junctions |
-Prevents fluids and most molecules from moving between cells |
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Desmosomes |
-"Rivets" or "spot-welds" that anchor cells together |
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Gap Junctions |
-Transmembrane proteins form pores that allow small molecules to pass from cell to cell |
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Membrane Transport |
-Plasma membranes are selectively permeable -Some molecules pass through the membrane; others do not |
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Types of Membrane Transport |
-Passive: No ATP required, moves substance down it concentration gradient -Active: ATP required, Occurs only in living cell membranes |
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Passive Processes |
-Simple diffusion -Carrier-mediated facilitated diffusion -Channel-mediated facilitated diffusion -Osmosis |
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What determines whether or not a substance can passively permeate a membrane? |
-Lipid solubility of substance -Channel of appropriate size -Carrier proteins |
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Simple Diffusion |
-Nonpolar lipid-soluble (hydrophobic) substances diffuse directly through the phospholipid bilayer |
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Facilitated Diffusion |
-Certain lipophobic molecules (like glucose, amino acids, and ions) use carrier proteins or channel proteins -Both proteins: -Exhibit specificity (selectivity) -Are saturable; rate is determined by number of carriers or channels -Can be regulated in terms of activity and quantity |
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Carrier Proteins |
-Transmembrane integral proteins transport specific polar molecules (like sugars and amino acids) -Binding of substrate causes shape change in carrier |
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Channel Proteins |
-Aqueous channels formed by transmembrane proteins selectively transport ions or water -Has two types: -Leakage channels (Always open) -Gated channels (controlled by chemical or electrical signals) |
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Osmosis |
-Movement of solvent (water) across a selectively permeable membrane -Water diffuses through plasma membranes through: -The lipid bilayer -Water channels called aquaporins (AQPs) -Water concentration is determined by solute concentration because solute particles displace water molecules -Osmolarity |
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Osmolarity |
-The measure of total concentration of solute particles -When solution of different osmolarity are separated by a membrane, osmosis occurs until equilibrium is reached |
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Importance of Osmosis |
-When osmosis occurs, water enters or leaves a cell -Change in volume disrupts cell function |
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Isotonic solution |
-Cells retain their normal size shape due to equilibrium |
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Hypertonic solution |
-Cells lose water by osmosis and shrink due to a higher concentration of solutes outside the cell than inside the cell |
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Hypotonic solution |
-Cells take in water by osmosis and become bloated and burst (lyse) due to a lower concentration of solutes outside the cell than inside the cell |
